It has previously been known that certain photochemical reactions may be performed more readily in an apparatus or a vessel which includes a provision for photoillumination of the reaction substrates, as well as their exposure to certain catalytic agents. For example, U.S. Pat. No. 3,476,667 discloses an apparatus for a photochemical reaction which includes a series of lamps disposed in the reaction vessel and suitable means to stir an appropriate solution within the reaction vessel to ensure mixing of reactives. Cooling tubes may also be provided in such a device to facilitate any necessary cooling to dissipate excess heat created by the energy released from the reaction.
Certain types of photochemical reactions in which the incident energy of reaction is provided by light radiation can be electrically biased to facilitate certain reaction products. At least one example is known, as shown in U.S. Pat. No. 4,124,464, of the use of a catalytic semiconductor anode in a water photolysis cell driven by incident solar radiation and in which the catalytic electrode is electrically biased so as to facilitate the hydrolysis of water in the desired reaction. It has been the previous practice in the art for such a reactor, which requires a transition metal electrode to properly catalyze the reaction, to fabricate the transition metal electrode in a single piece, the surface area of which is increased by scoring or other forms of indentation, such as disclosed in the above identified patent.
It has been previously demonstrated in the art that certain forms of metal oxide materials can be created which have a greatly enhanced surface area. One form of such metal oxide materials is known as a metal oxide ceramic membrane. The metal oxide ceramic membranes are typically formed of transition metal elements, such as titanium, silicon, zinc or other similar elements which have useful catalytic or photocatalytic properties. The metal oxide membranes are ceramic in that they are formed of a plurality of initially discrete particles which are fused together in a sintering or fusing process, usually by baking in an oven, to form a continuous unitary and solid material. Such metal oxide ceramic materials are referred to as membranes in that, when fired at appropriate temperatures (e.g. up to 550.degree. C. for TiO.sub.2 and 1000.degree. C. for Al.sub.2 O.sub.3), the resulting materials are porous, in the sense that materials may actually flow through the membranes if the support substrate is porous. Thus, the membranes may be thought of as analogous to biological membranes in that they are porous to materials of certain sizes, have a characteristic particle size and size of typical and maximum pores, but are by contrast formed of relatively rigid and stable inorganic metal oxide covalent bonds. It has been previously demonstrated, as exemplified by published PCT application WO 89/00985, and U.S. Pat. No. 5,035,784 that a metal oxide ceramic membrane can be usefully applied to the photodegradation of complex organic molecules. The use of ceramic membranes to treat waste streams to degrade environmental contaminants would be greatly facilitated if methods existed to regenerate such catalytic membranes as they become fouled, a regular occurrence in waste stream treatment.